How to check and eliminate the common faults of th

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How to check and eliminate common motor faults

AC motor will inevitably fail due to friction, vibration, insulation aging and other reasons during operation. If these faults are checked, found and eliminated in time, accidents can be effectively prevented

I. fault inspection of asynchronous motor

1. listen to the sound and carefully find the fault point. During the operation of AC asynchronous motor, if you find a thin "buzzing" sound, there is no change from high to low, it is a normal sound. If the sound is thick, and there is a sharp "buzzing" and "buzzing" sound, it is a precursor to the existence of faults, you should consider the following reasons around the revitalization goal:

(L) vibration of loose iron core motor in operation, The change of temperature from high to low will deform the fixing bolts of the iron core, cause the silicon steel sheet to loosen, and produce large electromagnetic noise

(2) rotor noise the sound made by the rotation of the rotor is produced by the cooling fan. It is a kind of "purring" sound, which is like the "thumping" sound when the drum is beating. This is caused by the low use rate of degradable plastic in the coordination between the rotor core and the shaft caused by the acceleration torque when the motor changes speed suddenly, stops, reversely brakes, etc. the light one can continue to be used, and the heavy one can be disassembled for inspection and repair

(3) bearing noise during the operation of the motor, attention must be paid to the culture of bearing sound. Touch one end of the screwdriver on the bearing cover and stick the other end to the ear. You can hear the sound changes inside the motor, different parts, different faults, and different sounds. For example, the "creak" sound is caused by the irregular movement of the rolling gun in the bearing, which is related to the clearance and grease state of the bearing. The "hissing" sound is the sound of metal friction, which is generally caused by the lack of oil in the bearing. The bearing should be disassembled and greased

2. Using bromine sense, it is analyzed that there is no peculiar smell in the normal operation of the faulty motor. If strange smell is smelled, it is a fault signal, such as burnt smell, which is sent by the barbecue of insulation. Specifically, it needs to communicate with after-sales personnel, and with the increase of motor temperature, it will smoke in serious cases; For example, the smell of oil burning is mostly due to the lack of oil in the bearing and the peculiar smell caused by the evaporation of oil and gas when it is close to the dry grinding state

3. use the hand feeling to check the fault. Touch the TV shell with your hand to roughly judge the temperature rise. If you touch the motor shell with your hand and feel very hot, the temperature value is very high, you should check the reasons, such as heavy load and high voltage, and then eliminate the fault according to the reasons

II. Causes of common faults

1. The motor has no starting torque, or cannot be started under no-load, and makes abnormal sound. Cause: (L) one phase of the three-phase power supply circuit (including knife switch and lead stator winding) is powered off, causing single-phase startup. (2) The power supply voltage is too low. (3) The bearing is excessively worn, which makes the rotor close to the side of the stator, resulting in the non concentricity of the stator and the rotor and uneven air gap

2. the starting torque of the motor is small, so it cannot be started when there is load. When the load increases, the motor stops, sometimes makes a strong noise, and local heating. Cause: the electric voltage is low, the winding has inter turn short circuit, there is wire break or desoldering in the rotor winding, and one phase wire break after startup causes single-phase operation

3. the starting current is large, unbalanced and loud, causing the protective device to act and cut off the power supply. Cause: the wiring method of stator winding may be incorrect, and the insulation of winding to ground is aging

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